HP Warranty Lookup using PowerShell SOAP

Up to recently the web scraping of HP warranty information worked fine, however in the last couple of weeks they have changed the web page and it seems they are using POST rather than GET now on the new page, meaning I can't really just pass the information to the URL.

I think everything will work as expected but I am struggling to form the request to register the client, I keep getting 500 errors which either means their server is broken or my request is causing an internal error.

I am for the first time completely at a loss with this.

Anybody got this to work in PowerShell or having similar issues?

Updated 22-10-13

I now have the envelope, I managed to get the Python script to run but that failed because of my proxy, so extracted the generated XML which is what I wanted as I wasn't sure how it should be formed, this looks like: